R. Machemehl and Millar, D., “Evaluation of the Spatial Distribution of Activity Center Parking Facilities,” Transportation Research Record, 1993.Abstract
D. J. Dixon and Johnston, K. P., “FORMATION OF MICROPOROUS POLYMER FIBERS AND ORIENTED FIBRILS BY PRECIPITATION WITH A COMPRESSED FLUID ANTISOLVENT,” Journal of Applied Polymer Science, vol. 50, pp. 1929-1942, 1993. Publisher's VersionAbstract
Polymer morphology is controlled over a continuum from microspheres to interconnected bicontinuous networks to fibers with a versatile new process: precipitation with a compressed fluid antisolvent. The results are explained qualitatively as a function of phase behavior, mass-transfer pathways, and the formation rates of skin on the flowing jet. By spraying dilute polystyrene in toluene solutions into liquid carbon dioxide, extremely small 100 nm microspheres are formed. For concentrations above the critical composition, fibers are produced that are not only microcellular, but, in some instances, even hollow. Mass-transfer pathways that cross the binodal near the critical composition produce interconnected networks, likely due to spinodal decomposition. In this region, fibers composed of highly oriented microfibrils are produced at high shear rates. Preaddition of CO2 influences the morphology because of dilution, in a similar manner as a liquid antisolvent, except that the viscosity reduction is larger due to added free volume. Because CO2 diffuses through the glassy polystyrene skin faster than does a conventional liquid antisolvent such as methanol, it produces more porous fibers, which are also more cylindrical. (C) 1993 John Wiley & Sons, Inc.
W. R. Hudson and Zhang, Z., “GIS Applications in Urban Roadway Management Systems,” Proceedings of the 5th International Conference on Computing in Civil and Building Engineering. American Society of Civil Engineers, Anaheim, CA, pp. Vol 1. pp 730-733, 1993.
S. G. Kazarian, Gupta, R. B., Clarke, M. J., Johnston, K. P., and Poliakoff, M., “HOW IS HYDROGEN-BONDING INFLUENCED BY SOLVENT DENSITY - THE SPECTROSCOPIC STUDY AND MODELING OF THE INTERACTION BETWEEN A PROTON DONOR AND ACCEPTOR FROM THE GAS-PHASE TO SUPERCRITICAL-FLUID STATES,” Journal of the American Chemical Society, vol. 115, pp. 11099-11109, 1993. Publisher's VersionAbstract
Fourier transform IR spectroscopy is used to study the effects of solvent density on the H-bonding equilibrium between perfluoro-tert-butyl alcohol (PFTB), (CF3)3COH, and dimethyl ether (DME), (CH3)2O, in solution in SF6 (T(c), 45.5-degrees-C; P(c), 540 psi; rho(c) 5.03 mol/L). The interaction of PFTB and DME is quite strong, and thus it has been possible to use rather more dilute solutions than in previous studies of H-bonding in supercritical fluids. Both PFTB and DME are highly volatile so the equilibrium could be studied over the full range of densities of SF6 from the pure gas phase (i.e. in the absence of SF6) through the supercritical region to liquidlike densities ca. 10 mol/L (1.5 gm/L) and over the temperature range 20-65-degrees-C. Both qualitative and quantitative measurements have been made at constant temperature, constant pressure, and constant density. The experiments introduce a number of innovative features both in methodology and in data manipulation. The modified lattice-fluid hydrogen-bonding model (MLFHB) has been used to calculate the effects of density on the percent of free (uncomplexed) PFTB in the solution and on the value of the equilibrium constant K(c). Qualitative studies show explicitly and without any spectroscopic assumptions that increasing density causes an increase in the concentration of free PFTB and a concomitant decrease in the concentration of the H-bonded PFTB/DME complex. More detailed measurements have allowed these changes to be quantified and modeled; particularly interesting are (a) the variation of K(c) with temperature at constant pressure (4.4 MPa), where the rapid increase in solvent density near the critical temperature cancels almost completely the effects of lowering the temperature and (b) the isothermal dependence of K(c) with density, including the unusual behavior at 50-degrees-C in the density range ca. 3-6 mol/L of SF6, behavior which is not observed at 60-degrees-C. This unusual behavior provides good evidence of enhanced solute-solute interactions toward the solvent critical temperature, as is further demonstrated with a simplified model.
D. G. Peck and Johnston, K. P., “LATTICE FLUID SELF-CONSISTENT FIELD-THEORY OF SURFACES WITH ANCHORED CHAINS,” Macromolecules, vol. 26, pp. 1537-1545, 1993. Publisher's VersionAbstract
Self-consistent field theory is combined with lattice fluid theory to produce a robust model of the structure and interactions of chains anchored to smooth surfaces. The inclusion of holes in the lattice provides a means to investigate the effects of bulk solvent density and temperature on the interfacial properties. In a good solvent at the incompressible limit, the interactions between the surfaces are repulsive but become attractive with the addition of free volume and compressibility, e.g. in alkane liquids. As density decreases, solvent is expelled from the higher density interfacial region to the lower density bulk phase. The solvent expulsion raises the entropy and increases the strength of the attractive interactions between the surfaces. This behavior is analogous to phase separation of bulk mixtures at the lower critical solution temperature. A novel result is that the forces between the surfaces become attractive at a much higher density than required for phase separation in bulk systems.
C. -Y., “Lee,” J. F. Bard, M. Pinedo and W. E. Wilhelm (1993). Guidelines for Reporting Computational Results in {IIE} Transactions. {IIE} Transactions, vol. 25, pp. 121–123, 1993.
F. J. Kuchuk, Habashy, T. M., and Torres–Verdín, C., “A Nonlinear Approximation for the Pressure Behavior of Heterogeneous Reservoirs (Expanded Abstract),” Proceedings of the 68th Annual Technical Conference and Exhibition of the Society of Petroleum Engineers. Society of Petroleum Engineers, Houston, TX, 1993.
F. J. Kuchuk, Habashy, T. M., and Torres–Verdín, C., “A Nonlinear Approximation for the Pressure Behavior of Heterogeneous Reservoirs (Expanded Abstract),” Proceedings of the 68th Annual Technical Conference and Exhibition of the Society of Petroleum Engineers. Society of Petroleum Engineers, Houston, TX, 1993.
J. A. Mullins, Rawlings, J. B., and Johnston, K. P., “PARTIAL DERIVATIVE QUANTITIES FROM PHASE-EQUILIBRIA RELATIONSHIPS FOR MIXTURES,” Aiche Journal, vol. 39, pp. 1363-1369, 1993. Publisher's VersionAbstract
A systematic formulation of multicomponent/multiphase phase equilibria as a linear algebra problem in the fugacities, mole fractions, partial molar volumes, and partial molar enthalpies is given. The algorithm takes advantage of the Gibbs-Duhem relationships for each phase and a modified Gaussian elimination technique to reduce the system of equations. These algorithmic steps allow current symbolic manipulation packages to generate useful partial derivative relationships in terms of measurable thermodynamic quantities. Features of the algorithm are demonstrated by applying a computer implementation of the method to a simple two-phase/two-component system and to the more complicated examples of a two-phase/three-component supercritical fluid chromatography experiment and a mass-conserving closed system.
G. J. McFann and Johnston, K. P., “PHASE-BEHAVIOR OF NONIONIC SURFACTANT OIL-WATER SYSTEMS CONTAINING LIGHT ALKANES,” Langmuir, vol. 9, pp. 2942-2948, 1993. Publisher's VersionAbstract
The phase behavior of nonionic ethoxylate surfactant/light alkane/water systems is reported in detail. In compressible liquids such as propane, phase transitions which are normally induced by changing temperature or salinity can also be accomplished with pressure A complete transition from a lower to middle to upper phase microemulsion with pressure is reported for the first time in propane. Widely accepted trends in surfactant phase behavior as a function of the alkane carbon number (ACN) of the oil component reverse themselves in the light alkanes butane, propane, and ethane. This pattern occurs in both reverse micelle systems (small water-to-oil ratio) and Winsor microemulsion systems (water-to-oil ratio near unity). The observed pressure and ACN effects can be explained qualitatively in terms of the miscibility gaps of the binary phase diagrams and quantitatively in terms of enthalpic and entropic interactions between the surfactant tails and the compressible solvent.
M. W. Fitch, Graham, D. W., Arnold, R. G., Agarwal, S. K., Phelps, P., and Speitel Jr, G. E., “Phenotypic Characterization of Copper-Resistant Mutants of Methylosinus trichosporium OB3b,” Applied and Environmental Microbiology, vol. 59, pp. 2771-2776, 1993.
P. D. Condo and Johnston, K. P., “PLASTICIZATION OF POLYMERS WITH COMPRESSED FLUID DILUENTS,” Abstracts of Papers of the American Chemical Society, vol. 205, pp. 153-PMSE, 1993. Publisher's VersionAbstract
D. J. Dixon, Johnston, K. P., and Bodmeier, R. A., “POLYMERIC MATERIALS FORMED BY PRECIPITATION WITH A COMPRESSED FLUID ANTISOLVENT,” Aiche Journal, vol. 39, pp. 127-139, 1993. Publisher's VersionAbstract
Polymer microspheres and fibers are formed with a versatile new process, precipitation with a compressed fluid antisolvent. By spraying a 1 wt. % polystyrene in toluene solution into CO2 through a 100-mum nozzle, microspheres are formed with diameters from 0.1 to 20 mum as the CO2 density decreases from 0.86 to 0.13 g/cm3. The uniform submicron spheres produced at high CO2 density are due in part to the rapid atomization produced by the large inertial and low interfacial forces. Fibers, with and without microporosity, are obtained at higher polymer concentrations where viscous forces stabilize the jet. The effect of CO2 density and temperature on the size, morphology and porosity of the resulting polymeric materials is explained in terms of the phase behavior, spray characteristics, and the depression in the glass transition temperature.
D. G. Peck and Johnston, K. P., “PREDICTION OF INTERFACIAL PROPERTIES IN MICROEMULSIONS - THE LATTICE FLUID SELF-CONSISTENT-FIELD THEORY,” Journal of Physical Chemistry, vol. 97, pp. 5661-5667, 1993. Publisher's VersionAbstract
A lattice fluid self-consistent field theory is used to calculate both the composition and fundamental thermodynamic properties, i.e., the interfacial tension (gamma) and bending moment (c), of spherical interfaces between oil and water. The variation in density throughout the interface is treated by the inclusion of holes in the lattice. This molecular theory is inserted into new classical thermodynamic expressions for gamma and c which take into account the fact that the surfactant tails are anchored to an interface. The detailed description of the composition throughout the interface provides a means to understand the effect of density and radius on the bending moment. The natural curvature and interdroplet interactions are calculated for water-in-propane microemulsions formed with the surfactant Aerosol-OT and compared with experiment.
B. I. Dvorak, Lawler, D. F., Speitel Jr, G. E., Jones, D. L., and Boadway, D. A., “Selection Among Treatment Technologies for Waters Contaminated with Synthetic Organic Chemicals,” Water Environment Research, vol. 65, no. 7, pp. 827-838, 1993.
J. F. Bard, Venkatraman, K., and Feo, T. A., Single Machine Scheduling with Flow Time and Earliness Penalties. Journal of Global Optimization 3, 1993, pp. 289–309.
R. B. Gupta, Combes, J. R., and Johnston, K. P., “SOLVENT EFFECT ON HYDROGEN-BONDING IN SUPERCRITICAL FLUIDS,” Journal of Physical Chemistry, vol. 97, pp. 707-715, 1993. Publisher's VersionAbstract
A pronounced solvent effect on the hydrogen bonding of methanol and triethylamine is observed throughout the gas, supercritical, and liquid states in the relatively inert solvent SF6, based on FTIR spectroscopy. The free energy of hydrogen bonding is stabilized by a decrease in density; i.e., the donor and acceptor are destabilized more than the complex as the solvation is reduced. Also, the hydrogen bond energy becomes stronger. A hydrogen-bonding lattice-fluid (LFHB) model is extended to treat this density dependence, and the calculations are in reasonable agreement with experiment. Near the mixture critical point, the number of hydrogen bonding encounters between the donor and acceptor is enhanced due to solute-solute clustering as expected on the basis of previous experimental and computer simulation studies.
A. I. Cooper, Howdle, S. M., Hughes, C., Jobling, M., Kazarian, S. G., Poliakoff, M., Shepherd, L. A., and Johnston, K. P., “SPECTROSCOPIC PROBES FOR HYDROGEN-BONDING, EXTRACTION IMPREGNATION AND REACTION IN SUPERCRITICAL FLUIDS,” Analyst, vol. 118, pp. 1111-1116, 1993. Publisher's VersionAbstract
Spectroscopy is used for monitoring a number of processes relevant to solution, extraction and impregnation in supercritical CO2 (scCO2). Examples include: a combined infrared (IR) and ultraviolet study of the interaction between para-hydroquinone (HQ) and tributyl phosphate in scCO2, which reveals hydrogen bonding, detected by the characteristic nu(O-H) IR bands; IR measurement of the solubility of CpMn(CO)3 (CP = eta5-C5H5) in SCCO2 as a function of temperature and pressure; an investigation of the uniformity of supercritical impregnation of CpMn(CO)3 into 4 mm diameter pellets of polyethylene (PE) using Fourier-transform infrared (FTIR) microscopy and FTIR depth profiling by photoacoustic detection; and an IR study of the photochemical reaction of CpMn(CO)3 with N2 with PE film.
T. Rioux, Inman, R., Machemehl, R. B., and Lee, C. L., “Texas model for intersection traffic-additional features,” 1993.Abstract